Silicone rubber compositions containing novel/ketoxime-based silanes

ABSTRACT

The invention relates to the following novel silanes: methyl vinyl bis-(methyl isobutyl ketoximino) silane; methyl vinyl bis-(methyl amyl ketoximino) silane; methyl tris-(methyl isobutyl ketoximino) silane; vinyl tris-(methyl isobutyl ketoximino) silane; methyl tris-(methyl amyl ketoximino) silane; vinyl tris-(methyl amyl ketoximino) silane; tetrakis-(methyl isobutyl ketoximino) silane; tetrakis-(methyl amyl ketoximino) silane and mixtures thereof. These compounds are useful as intermediates in one-component room-temperature-curing sealant, adhesive and coating applications among other silicone polymer applications.

This application is a division of application Ser. No. 07/947,015, filedSep. 17, 1992, now U.S. Pat. No. 5,359,108.

BACKGROUND OF THE INVENTION

A variety of useful silicone compositions cure at room temperature toelastomeric materials which possess a broad spectrum of physical andchemical properties. These compositions are particularly desirablebecause they surface cure in thirty minutes or less after exposure tothe atmosphere but remain substantially soft for years. They also adheretenaciously to a wide variety of materials such as glass, porcelain,wood, metal and organic plastics. Because of this, they are adaptablefor practically any type of sealant application including building andautomotive equipment applications. The following patents discuss some ofthese compounds in more detail.

U. S. Pat. No. 3,189,576 to Sweet describes oxime silanes useful in themanufacture of room temperature curing compositions. Specifically, Sweetteaches trifunctional and tetrafunctional ketoximino silanes ascrosslinkers and their use in the manufacture of room temperature curingsilicone elastomeric compositions by mixing them with hydroxylendblocked polydiorganosiloxanes. These compositions can also containfillers and curing catalysts.

U.S. Pat. No. 4,503,210 to Von Au discloses mixtures of tri- andtetrafunctional ketoximino silanes and focuses specifically on theusefulness of tetrafunctional ketoximino silanes in sealantformulations.

The problem with known tetrafunctional oximino silanes (i.e., e.g.,those based on methyl ethyl ketoxime (MEKO) and acetone oxime) is thatthey are solids at room temperature. Since such compounds are verysensitive to moisture they decompose easily to semisolids which aredifficult to handle. Thus, these materials have a poor shelf life andrequire special care in their packaging and transporting.

The known tetrafunctional and trifunctional oximino silanes (i.e., e.g.,those based on MEKO and acetone oxime) have other drawbacks.Traditionally, when these materials have been combined with siliconepolymers the resulting product has been opaque. This has substantiallylimited the applications in which these materials can be used.

As the applications in which room temperature curing compositions can beutilized continue to increase, the specific kinds of properties requiredof these compositions continue to change. The art is continually lookingfor room temperature curing compositions having new desirable propertieswithout the old undesirable properties like opacity and physical statelimitations (solids). We have surprisingly discovered that the silanesof the invention satisfy this need in the art.

DESCRIPTION OF THE INVENTION

The invention relates to silanes of the formula:

    (R.sub.2 C=NO).sub.a SiR.sup.1.sub.4-a

where R is any saturated straight chain or branched alkyl radical of 1to 7 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl and amyl, R¹ is any saturated, straight chain alkyl radical of1 to 5 carbon atoms such as methyl, ethyl and propyl or an alkenylradical of 1 to 5 carbon atoms such as methyl, vinyl and allyl and a isa positive integer ranging in value from 2 to 4. More specifically, theinvention relates to the following silanes: methyl vinyl bis- (methylisobutyl ketoximino) silane; methyl vinyl bis-(methyl amyl ketoximino)silane; methyl tris-(methyl isobutyl ketoximino) silane; vinyltris-(methyl isobutyl ketoximino) silane; methyl tris-(methyl amylketoximino) silane; vinyl tris-(methyl amyl ketoximino) silane;tetrakis-(methyl isobutyl ketoximino) silane; tetrakis-(methyl amylketoximino) silane and mixtures thereof.

As currently used in sealant compounding, commercial tetra-functionaloximino silanes are either mixed (dissolved) in trifunctional oximinosilanes as described in U.S. Pat. 4,503,210 or dissolved in organicsolvents.

In the former case solubility limits the level of tetrafunctionaloximino silane in the trifunctional oximino silane to 35-40% at roomtemperature. This is disadvantageous because higher levels oftetrafunctional oximino silane increase cure rate and minimize (if noteliminate) the need for a catalyst.

In the latter case, solid tetrafunctional oximino silanes are mixed withhydrocarbons like toluene, benzene and xylene, organic ethers likediethylether and dibutylether, ketones and halogenated solvents tofacilitate ease of handling in applications which require preciseamounts of tetrafunctional oximino silane. Because some of thesesolvents are flammable and carcinogenic, further precautions must betaken to ensure the safety of personnel during processing. In addition,one must ensure that the vapor emissions from the finished sealantproducts generated during end use are safe for people and theenvironment. These precautions are both costly and time consuming.

Solubility is also a concern. That is, for example, at room temperature,tetrafunctional MEKO-based silane is only 50% soluble in toluene and inmethyl ethyl ketoxime, 40% soluble in diethyl ether and 10% soluble indibutyl ether. As a result, significant amounts of solvent may berequired in the formulation. In addition, crystallization can occur atlower temperatures (i.e., e.g., during shipping in winter months) and athigher concentrations of the tetrafunctional oximino silane.

Because of this, there has been a long felt need in the industry fortetrafunctional oximino silanes which do not require organic solvents ormixing with trifunctional oximino silanes. We have surprisinglydiscovered that the novel tetrakis oximino silanes of our invention,i.e, tetrakis-(methyl isobutyl ketoximino) silane and tetrakis-(methylamyl ketoximino) silane are liquids and thus do not suffer with the sameproblems as their solid counterparts.

This is surprising since generally, physical states of organic compoundstransform from gas to liquid to solid as molecular weight increases in ahomologous series. See, R. T. Morrison and R. N. Boyd, OrganicChemistry, 91-4 (5th Ed. 1987). For example, in the aliphatichydrocarbon series, lower molecular weight compounds like propane (MW44) and butane (MW 58) are gases, higher molecular weight hydrocarbonslike hexane (MW 86) and octane (MW 114) are liquids and the long chainhydrocarbon paraffins like eicosane (MW 282.6), docosane (MW 316.6) andtetracosane (MW 338.7) are solids.

In the instant case, since tetrafunctional oximino silanes of lowermolecular weight alkyl ketoximes like acetone oxime (MW 73) and methylethyl ketoxime (MW 87) are solids, we also expected tetrafunctionaloxime silanes of methyl isobutyl ketoxime and methyl amyl ketoxime whichhave higher molecular weights (115 and 129 respectively) to be solids.However, surprisingly, during our synthesis of these materials wediscovered that both tetrakis-(methyl isobutyl ketoximino) silane andtetrakis-(methyl amyl ketoximino) silane are liquids at roomtemperature.

We have also discovered unexpectedly, that when oximino silanes of theinvention are formulated with hydroxyl terminated polydimethylsiloxane(HTPDMS), a well known silicone polymer, an optically clear siliconerubber results. This is surprising because generally when commerciallyavailable oxime silanes have been combined in typical and usefulconcentrations with silicone polymers, a very cloudy and opaque rubberresults. (Compare Examples 1-9 with Comparative Examples 1-4 below).This has limited the number of applications in which these materials canbe utilized. In light of our discovery, the door is now open to avariety of applications in which aesthetics are important and from whichoxime silanes have traditionally been excluded.

The novel ketoximino silanes of the invention may be prepared byfollowing the syntheses outlined below. See, U.S. Pat. No. 4,400,527.Alternately, they may be prepared by any means known in the art. We notethat the oximes used in the syntheses below may be prepared by any meansknown in the art. See, for example, the syntheses outlined in U.S. Pat.Nos. 4,163,756 and 3,991,115 both to Allied-Signal Inc.

Preparation of tetrakis-(methyl isobutyl ketoximino) silane

A 1 liter 3-necked flask equipped with a condenser, thermometer anddropping funnel was charged with 350 ml of hexane and 96.7 g (0.84 mol)of distilled methyl isobutyl ketoxime. A drierite tube was attached tothe condenser to ensure a dry reaction medium. The reaction flask wasthen placed in a cold water bath. While the hexane/ketoxime solution wasstirred using a magnetic stirrer, 17 g (0.1 mol) tetrachloro silane wasadded dropwise into the reaction flask. The reaction temperature wasmaintained between 35° and 42° C. during the addition. After theaddition of tetrachloro silane was complete, the reaction mixture wasstirred for 5 minutes and then allowed to settle for 5 minutes. Thecolorless hexane solution top phase was separated from the viscousmethyl isobutyl ketoxime hydrochloride bottom phase using a separatoryfunnel. The top phase was then treated with anhydrous ammonia gas from acylinder for 10 minutes. The solid ammonium chloride that separated outwas filtered off and the colorless filtrate was subjected todistillation under reduced pressure (50° C. at 5 mm Hg) on a rotovap toremove hexane. About 42 g (86%) yield) of a colorless liquid wasobtained. The identity of this material as tetrakis-(methyl isobutylketoximino) silane was confirmed by proton and carbon-13 NMR and GC/Massspectral data.

Preparation of tetrakis-(methyl amyl ketoximino) silane.

A 2 liter three-necked round bottom flask, fitted with an additionfunnel, condenser and thermometer, was charged with 1300 ml of hexaneand 418.6 g (3.24 mol) of methyl amyl ketoxime. While the solution wasbeing stirred by means of an overhead stirrer, 67.96 g (0.4 mol) oftetrachloro silane was added dropwise over a period of 30 minutes duringwhich time the reaction temperature was kept between 37°-42° C. Afterthe tetrachloro silane had been added, the reaction mixture was allowedto stand for five minutes. The cloudy top phase was separated from themethyl amyl ketoxime hydrochloride bottom phase using a separatoryfunnel. Then, the top phase was neutralized with anhydrous ammonia overa period of 15 minutes and the solid ammonium chloride produced wasfiltered off. The hexane was removed from the filtrate under vacuum togive 178.5 g (82.6%) of a liquid. The identity of this liquid wasconfirmed as tetrakis-(methyl amyl ketoximino) silane by IR and protonand carbon-13 NMR spectral data.

Preparation of methyl tris-(methyl isobutyl ketoximino) silane,

A 5 liter, three-necked and water jacketed flask, fitted withthermometer, overhead stirrer and addition funnel, was charged with714.3 g (6.20 mol) of methyl isobutyl ketoxime and 3000 ml of hexane.One mole or 149.48 g of methyltrichlorosilane was added dropwise over aperiod of 1 hour during which the reaction temperature was maintainedbetween 37°-42° C. After the addition of methyltrichlorosilane wascomplete, the reaction mixture was stirred for 5 minutes and allowed tostand for 10 minutes. The top phase was separated from the methylisobutyl ketoxime hydrochloride bottom phase using a separatory funneland neutralized with ammonia gas by bubbling the ammonia through theliquid for 10 minutes. Solid ammonium chloride was filtered off andhexane was removed from the filtrate by vacuum distillation to give 380g (98.7%) of a colorless liquid. The identity of the product as methyltris-(methyl isobutyl ketoximino) silane was confirmed by IR and protonand carbon-13 NMR spectral data.

Preparation of vinyl tris-(methyl isobutyl ketoximino) silane.

A 3 liter, three-necked, round bottomed flask equipped with an overheadstirrer, thermometer and addition funnel was charged with 714.0 g (6.20mol) of methyl isobutyl ketoxime and 1200 ml of hexane. While stirring,161.5 g (1.0 mol) of vinyltrichlorosilane was added dropwise over aperiod of 1 hour and the reaction temperature was maintained between37°-41° C. After the addition was complete, the reaction mixture wasallowed to stand for 10 minutes. The top phase containing product andhexane was separated from the bottom phase (methyl isobutyl ketoximehydrochloride) using a separatory funnel and neutralized with ammoniagas for 10-15 minutes. Solid ammonium chloride was filtered off andhexane was removed from the filtrate by distilling under reducedpressure to give 374 g (94%) of a colorless liquid. The identity of thisliquid as vinyl tris-(methyl isobutyl ketoximino) silane was confirmedby IR and proton and carbon-13 NMR spectral data.

Preparation of methyl tris-(methyl amyl ketoximino)

A 2 liter, three-necked, round bottomed flask, fitted with athermometer, overhead stirrer and addition funnel was charged with 394.1g (3.05 mol) of methyl amyl ketoxime and 1000 ml of hexane. Whilestirring the contents in the flask, 74.5 g (0.5 mol) ofmethyltrichlorosilane was added dropwise from the addition funnel over aperiod of 30 minutes. During the addition, the reaction temperature wasmaintained at 35°14 41° C. After the addition was complete, the reactionmixture was allowed to stand for 10 minutes. The top phase containinghexane and the product was separated from the heavy methyl isobutylketoxime hydrochloride bottom phase using a separatory funnel. The topphase was neutralized with ammonia gas by bubbling the ammonia throughthe liquid for 10 minutes. Solid ammonium chloride was filtered off andhexane was removed from the filtrate by distillation under reducedpressure to give 201.8 g (94.5%) of a colorless liquid. This liquid wasidentified by IR and proton and carbon-13 NMR spectral data as methyltris-(methyl amyl ketoximino) silane.

Preparation of vinyl tris-(methyl amyl ketoximino) silane.

A 2 liter, three-necked flask fitted with overhead stirrer, additionfunnel and thermometer was charged with 236.4 g (1.83 mol) of methylamyl ketoxime and 800 ml of hexane. While the contents of the flask werestirred, 48.45 g (0.3 mol) of vinyl-trichlorosilane was added dropwisefrom the addition funnel over a period of 30 minutes during which thereaction temperature was maintained between 32°-41° C. After theaddition of vinylchlorosilane was complete, the reaction mixture wasallowed to stand for 10 minutes. The top phase containing product andhexane was separated from the heavy bottom phase (methyl amyl ketoximehydrochloride) using a separatory funnel and neutralized with ammoniagas by bubbling the ammonia through the liquid for 10 minutes. Ammoniumchloride was filtered to give a clear filtrate. Hexane was removed fromthe filtrate by distilling under reduced pressure to give 115 g (87%) ofa colorless liquid which was identified as vinyl tris-(methyl amylketoximino) silane by IR and proton and carbon-13 NMR spectral data.Preparation of methyl vinyl bis-(methyl isobutyl ketoximino) silane

Into a 500 ml, three-necked flask, fitted with thermometer, condenserand dropping funnel, was charged a solution of 47.17 g (0.41 mol) ofmethyl isobutyl ketoxime and 250 ml of hexane. While stirring thismixture by means of a magnetic stirrer, 14.11 g (0.1 mol) of methylvinyl dichlorosilane was added dropwise from the addition funnel over aperiod of 15 minutes. The reaction temperature was maintained between33°-38° C. After the addition of chlorosilane was complete, the reactionmixture was allowed to stand for 5 minutes during which the phasesseparated. The top phase was separated from the oxime hydrochloridebottom phase by means of a separatory funnel. The top phase wasneutralized with ammonia gas by bubbling the ammonia through the liquidfor 10 minutes and the precipitated ammonium chloride was filtered off.Hexane from the filtrate was removed by distillation under reducedpressure to give 27.5 g (89%) of a colorless liquid which was identifiedas methyl vinyl bis-(methyl isobutyl ketoximino) silane by IR and protonand carbon-13 NMR spectral data.

Preparation of methyl vinyl bis-(methyl amyl ketoximino) silane,

A 3 liter, three-necked flask fitted with an overhead stirrer, additionfunnel and thermometer was charged with 529 g (4.1 mol) of methyl amylketoxime and 1200 ml of hexane. While stirring the contents of theflask, 141 g (1.0 mol) of methyl vinyl dichlorosilane was added dropwisefrom the addition funnel over a period of 40 minutes during which thereaction temperature was maintained between 28°-32° C. After theaddition was complete, the reaction mixture was allowed to stand for 10minutes to form two phases. The top phase containing product and hexanewas removed from the oxime hydrochloride heavy phase using a separatoryfunnel and neutralized with ammonia gas by bubbling the ammonia throughthe liquid for 10 minutes. Ammonium chloride solid was filtered andhexane was removed from the filtrate by distillation under reducedpressure to give 286 g (87.7%) of a colorless liquid. This liquid wasidentified as methyl vinyl his- (methyl amyl ketoximino) silane by IRand proton and carbon-13 NMR spectral data.

EXAMPLE 1

To a 100 ml beaker was added 50 parts by weight of hydroxyl terminatedpolydimethylsiloxane (HTPDMS) having a viscosity of 50,000 cst. Then,1-4 parts by weight of methyl tris-(methyl isobutyl ketoximino) silane(prepared in accordance with the synthesis disclosed herein) was added.The compounds were mixed at 25° C. at 200 rpm using a standardlaboratory stirrer for 5 minutes. The resulting product cured to a clearsilicone rubber.

EXAMPLE 2-9

The experiment outlined in Example 1 above, was repeated using thefollowing silanes:

1.) 1-4 parts by weight methyl tris-(methyl amyl ketoximino) silane;

2.) 2-3 parts by weight vinyl tris-(methyl amyl ketoximino) silane;

3.) 2-3 parts by weight vinyl tris-(methyl isobutyl ketoximino silane);

4.) 1-3 parts by weight tetrakis-(methyl amyl ketoximino) silane;

5.) 1-3 parts by weight tetrakis-(methyl isobutyl ketoximino) silane;

6.) 3:1 parts by weight of a mixture of methyl is-(methyl isobutylketoximino) silane and tetrakis-(methyl isobutyl ketoximino) silane;

7.) 3:1 parts by weight of a mixture of methyl tris-(methyl amylketoximino) silane and tetrakis-(methyl amyl ketoximino) silane;

8.) 3:1 parts by weight of a mixture of methyl tris-(methyl amylketoximino) silane and tetrakis-(methyl isobutyl ketoximino) silane; Theresults were the same as those reported in Example 1. That is, theresulting cured silicone rubber was clear.

Comparative Example 1

To a 100 ml beaker was added 50 parts by weight of HTPDMS, having aviscosity of 50,000 cst. Then, 3-4 parts by weight of methyltris-(methyl ethyl ketoximino) silane was added. The compounds weremixed at 25° C. and 200 rpm using a standard laboratory stirrer for 5minutes. The resulting product cured to an opaque, cloudy siliconerubber.

Comparative Examples 2-4

The procedure outlined in Comparative Example 1 was repeated using thefollowing silanes:

1.) 2-10 parts by weight vinyl tris-(methyl ethyl ketoximino) silane;

2.) 3-10 parts by weight tetrakis-(methyl ethyl ketoximino) silane intoluene;

3.) 3:1 parts by weight of a mixture of methyl tris-(methyl ethylketoximino) silane and tetrakis-(methyl ethyl ketoximino) silane. Theresults are the same as those reported for Comparative Example 1. Thatis, the resulting product cured to an opaque, cloudy silicone rubber.

The silanes of the invention have utility as intermediates in thepreparation of various one-component room-temperature-curingcompositions for sealant, adhesive, coating and other silicone polymerapplications. These one-component systems may be prepared in accordancewith the teachings of U.S. Pat. No. 3,189,576 to Sweet (Example 17 atcol. 12, lines 6-26) and U.S. Pat. No. 4,720,530 to Wurminghause et al.at col. 1, lines 60-67 and col. 2, lines 1-43 which disclosure is herebyincorporated herein by reference. Generally, the method for preparingone-component room-temperature-curing compositions comprises reacting inthe substantial absence of moisture a hydroxy-endblocked siloxanepolymer with a silane. Optionally, fillers such as silica, chalk andglass beads, adhesion promotors such as organofunctional silanes andcatalysts such as tin carboxylates, dibutyl tin diacetate, and dibutyltin dilaurate, lead carboxylates, zinc carboxylates and organo titanatesmay be included in these formulations.

What is claimed:
 1. A liquid silicone composition comprising thereaction product of a hydroxy-endblocked siloxane polymer with a mixtureof at least one silane selected from the group consisting oftetrakis-(methyl isobutyl ketoximino) silane; tetrakis-(methyl amylketoximino) silane plus at least one ketoxime silane of the formula: (R₂C=NO)_(a) SiR¹ _(4-a) wherein R is any saturated straight chain orbranched alkyl radical of 1 to 7 carbon atoms, R1 is any alkyl oralkenyl radical of 1 to 5 carbon atoms and a is a positive integerranging in value from 2 to 4, and mixtures thereof.
 2. A siliconecomposition which comprises a substantially clear, liquid reactionproduct of a hydroxy-endblocked siloxane polymer and one or moresubstantially clear, liquid ketoxime silanes selected from the groupconsisting of methyl vinyl bis-(methyl isobutyl ketoximino) silane;methyl vinyl bis(methyl amyl ketoximino) silane; methyl tris-(methylisobutyl ketoximino) silane; vinyl tris(methyl isobutyl ketoximino)silane; methyl tris-(methyl amyl ketoximino) silane; vinyl tris(methylamyl ketoximino) silane; tetrakis-(methyl isobutyl ketoximino) silane;tetrakis-(methyl amyl ketoximino) silane.
 3. The silicone composition ofclaim 2 wherein the ketoxime silane is methyl tris-(methyl isobutylketoximino) silane.
 4. The silicone composition of claim 2 wherein theketoxime silane is vinyl tris-(methyl isobutyl ketoximino) silane. 5.The silicone composition of claim 2 wherein the ketoxime silane ismethyl tris-(methyl amyl ketoximo) silane.
 6. The silicone compositionof claim 2 wherein the ketoxime silane is vinyl tris-(methyl amylketoximino) silane.
 7. The silicone composition of claim 2 wherein theketoxime silane is tetrakis-(methyl isobutyl ketoximino) silane.
 8. Thesilicone composition of claim 2 wherein the ketoxime silane istetrakis-(methyl amyl ketoximino) silane.
 9. The silicone composition ofclaim 2 wherein the ketoxime silane is methyl vinyl bis-(methyl isobutylketoximino) silane.
 10. The silicone composition of claim 2 wherein theketoxime silane is methyl vinyl bis-(methyl amyl ketoximino) silane. 11.The silicone composition of claim 2 wherein the ketoxime silane is amixture of tetrakis-(methyl amyl ketoximino) silane and methyltris-(methyl amyl ketoximino) silane.
 12. A ketoxime silane compositionwhich comprises a mixture of tetrakis-(methyl isobutyl ketoximino)silane and methyl tris-(methyl isobutyl ketoximino) silane.
 13. Aketoxime silane composition which comprises a mixture oftetrakis-(methyl isobutyl ketoximino) silane and methyl tris-(methylamyl ketoximino) silane.
 14. A liquid ketoxime silane compositioncomprising a mixture of at least one ketoxime silane selected from thegroup consisting of tetrakis-(methyl isobutyl ketoximino) silane andtetrakis-(methyl amyl ketoximino) silane plus at least one ketoximesilane of the formula (R₂ C=NO)_(a) SiR¹ _(4-a) wherein R is anysaturated straight chain or branched alkyl radical of 1 to 7 carbonatoms, R1 is any alkyl or alkenyl radical of 1 to 5 carbon atoms and ais a positive integer ranging in value from 2 to 4, and mixturesthereof.
 15. The liquid ketoxime silane composition of claim 14comprising a mixture of tetrakis-(methyl isobutyl ketoximino) silaneplus at least one ketoxime silane selected from the group consisting ofmethyl vinyl bis-(methyl isobutyl ketoximino) silane; methyltris-(methyl isobutyl ketoximino) silane and vinyl tris(methyl isobutylketoximino) silane.
 16. The liquid ketoxime silane composition of claim14 comprising a mixture of tetrakis-(methyl amyl ketoximino) silane plusat least one ketoxime silane selected from the group consisting ofmethyl vinyl bis-(methyl amyl ketoximino) silane; methyl tris-(methylamyl ketoximino) silane and vinyl tris(methyl amyl ketoximino) silane.17. A method of making a one-component room-temperature-curing systemcomprising reacting in the substantial absence of moisture ahydroxy-endblocked siloxane polymer with one or more substantiallyclear, liquid ketoxime silanes selected from the group consisting ofmethyl vinyl bis-(methyl isobutyl ketoximino) silane; methyl vinylbis(methyl amyl ketoximino) silane; methyl tris-(methyl isobutylketoximino) silane; vinyl tris(methyl isobutyl ketoximino) silane;methyl tris-methyl amyl ketoximino) silane; vinyl tris(methyl amylketoximino) silane; tetrakis-(methyl isobutyl ketoximino) silane;tetrakis-(methyl amyl ketoximino) silane.